Destiny, a small black Retriever, insistently nudged Breanne, her person, who was sleeping soundly. Over and over, she pushed her warm snout into Breanne’s face, finally jolting her into wakefulness with bristly whiskers and a wet tongue. Breanne has Type 1 diabetes, and Destiny alerted her to the fact that her blood sugar levels were plummeting into dangerous territory. This special pup represents the newest “breed” of service dogs, one who detects hypoglycemia and offers hope, freedom and better health to those with Type 1 diabetes.

Breanne Harris is a 22-year-old student at UC Davis and has lived with Type 1 diabetes since she was four. In those with Type 1 (sometimes called “juvenile”) diabetes, the pancreas doesn’t produce insulin, a hormone that regulates the conversion of glucose (blood sugar) into energy. Instead, the diabetic needs to obtain this vital substance from injections or an insulin pump. Type 1 diabetics walk a perilous tightrope as they juggle food and insulin, aiming for blood sugar readings of between 80 and 150, measured with a tiny, handheld glucose meter.

Many factors influence blood glucose levels. Too much—or not enough—insulin, food or exercise, as well as stress or illness, can easily upset the balance. Sometimes, in spite of the most diligent management, blood sugar runs dangerously high or low for no apparent reason, and this can have serious health consequences. Blood sugar that runs high over an extended period of time can damage vision, organs and limbs, so the diabetic tries to keep blood glucose as close to the “normal” range as possible. But vigilance can inadvertently lead to episodes of hypoglycemia, or “lows,” that result in unconsciousness, seizure, coma and even death; the lower the individual’s blood sugar goes, the less able he or she is to take the steps needed to raise it to a safe level.

Here’s where the hypoglycemia-detecting service dog can make a life-or-death difference. Dogs4Diabetics[4] (D4D), a nonprofit organization based in Concord, Calif., is pioneering cutting-edge work with service dogs trained to alert their people or handlers to impending hypoglycemia. D4D founder Mark Ruefenacht first made the connection between dogs and diabetes eight years ago while training a puppy for Guide Dogs for the Blind.

One night, the puppy’s urgent whining awoke him. Mark, a diabetic, recognized the signs that his blood sugar was dropping rapidly. He also realized that the puppy had somehow detected the impending low. Trained in forensic metrology (the science of measurement), Mark began to explore the possibility of teaching dogs to detect low blood sugar. “We spent the next five years doing a lot of research to figure out how we could start a program,” he explains. “No medical instrument in the world can do what the dogs are doing with their noses.”

D4D dogs are generally career-change dogs from Guide Dogs for the Blind in nearby San Rafael, Calif. The dogs are highly trained by the time they arrive at D4D, and the intensive, specialized instruction they then receive, similar to the training for drug-detecting dogs, is customized to each dog’s learning strength. Without going into specific protocols, trainer Blancette Reynolds describes the “fluidity” that is essential to successful training: “Anything you do with any living creature is fluid, a work in progress. Sometimes I will modify my particular response to reinforce a particular behavior. And the criterion for each dog is a little different; for example, the bar is lower for a new dog.” The dogs’ training is so specific and comprehensive that they learn to expect a reward only after their handler or person has pulled out the glucose meter, tested his or her blood sugar, and gotten something to eat or drink. Only then do they receive that rewarding bit of kibble.

D4D dogs are trained to alert their handler when they detect a scent on the breath or in the sweat of someone whose blood glucose is dropping rapidly. The dogs can detect the scent from anyone nearby who might be “going low,” although they are trained to only alert their handler. The dogs graduate from the program when they can detect the scent with a 95 percent accuracy rate from across a room. Each dog alerts his handler with unique body language. After picking up the scent by snuffling loudly and inhaling as many telltale molecules as possible, Destiny alerts Harris by placing her paws on Harris’s lap or chest.

On Tuesday nights at D4D, dogs and their potential handlers test the waters with one another. People are focused and hopeful as they learn how to handle a dog and what to expect in public when accompanied by a service dog. Meanwhile, staff members are on the lookout for a special connection. “Many people are eager to be partnered with one of our dogs,” says director Carol Edwards. “But we don’t make placements according to a waiting list; instead, we pair up dogs and people when we see a special chemistry at work.” Once a match has been made, the dog and his handler work as a leashed-together pair 24 hours a day for up to two months. During this “umbilical period,” the dog learns to connect his person’s hypoglycemic scent with a reward. Reynolds explains, “It’s almost as if they are saying, I smell the scent. I’m going to let you know that I smell the scent, and then I’ll get treats!

At first, Harris didn’t believe that a dog could detect low blood sugar, but her skepticism vanished when she worked at a camp for diabetic children and accompanied a D4D dog on his midnight rounds. She became a believer when she watched the dog alert his handler to a sleeping child whose blood sugar reading was in the low 30s.

Just three weeks before the momentous night—the night when she didn’t wake up freezing in sweat-soaked linens—Harris brought Destiny home. Instead of ravenously raiding the refrigerator and experiencing the disorientation and emotional rollercoaster that accompanies midnight hypoglycemia, she simply lay in bed and drank a glass of juice. “It’s the best low I’ve ever had,” she confesses with a smile.

These days, Destiny accompanies Harris everywhere, wearing the blue vest that identifies her as a medical-alert service dog. Destiny’s presence in the car eliminates Harris’s concern about going low while driving, and in the classroom, Destiny sits by Harris’s side and gives her enough warning that she can grab a healthy snack without missing a moment of instruction. And at night, this faithful companion frees Harris to sleep soundly without the risks and fears of nighttime hypoglycemia.

The work at D4D holds promise for hundreds of thousands of Type 1 diabetics. For Mark and the other tireless volunteers at D4D, the bottom line is that these dogs relieve people of the fear of hypoglycemia, and they save lives. Most rewarding are the phone calls from parents who say, “The dog woke me up last night, and my child’s blood glucose was 40.”

Harris grew up with Lab mixes, and initially she looked forward to building a special relationship with her new dog; then she realized exactly how special that relationship would be: “When I first received Destiny, I was so excited to be able to care for a dog. This is really cool! I thought to myself. She depends on me for fun, for play, for food, for a good walk. But when she started to alert on me, it really struck home: I am the one who depends on her to literally save my life.” No glucose meter in the world can measure the depth of that bond.